1. Field of the Invention
The present invention relates to a touch panel and a display device including a touch panel.
2. Description of the Background Art
A touch panel that detects a touch of an indicator such as a finger and specifies positional coordinates of the touch is attracting attention as one of excellent user interface means. Touch panels according to various systems such as resistance film systems and electrostatic capacitance systems are commercialized.
As one of electrostatic capacitance systems, there is a PCT (Projected Capacitive Touchscreen) system that can perform touch detection even when a front surface side of a touch screen in which a touch sensor is incorporated is covered with a protection plate like a glass plate having a thickness of about a few millimeters (refer to Japanese Unexamined Patent Application Publication No. H09-511086 (1997), p. 7 line 19 to p. 8 line 4, p. 8 line 23 to p. 9 line 6, p. 13 lines 4 to 12, and see FIGS. 1, 2, and 8, for example). Because this system can have the protection plate arrayed on the front surface, the system has an advantage in that the system has excellent robustness, can detect a touch even when an operator is wearing gloves, and has a long life because there is no moving part.
For example, the touch screen of the touch panel using the PCT system described in Japanese Unexamined Patent Application Publication No. H09-511086 (1997) includes a first-series conductive material pattern (a conductor element) formed on a thin dielectric film and a second-series conductive material pattern (a conductor element) formed via an insulating film, as detection wirings for detecting electrostatic capacitances. Between the conductor elements, there is no electric contact, and a plurality of intersections are formed. Materials suited for conductive materials are metal materials such as silver, for example. Visibility becomes a problem in displaying. To reduce visibility, indium tin oxide (ITO) is used. A thin electric wire of 10 μm to 20 μm can be also used in place of a conductive material pattern.
A conductor element that detects electrostatic capacitances is connected to a capacitance control oscillator via an output line and a multiplexer. Outputs of the conductor element are counted by a divider, and are used as capacitance detection data.
In Japanese Patent Application Laid-Open Publication No. 2010-257178 (p. 5 lines 10 to 17, FIG. 4) described below, there is proposed a technique for providing a dummy drawing wiring at a further outer end of an outermost leading line, out of a plurality of leading lines that connect between a detection wiring and a terminal, on a touch screen of a touch panel. On the touch panel, a deviation between a parasitic capacitance of an outermost leading line and a parasitic capacitance of other leading line is suppressed, by applying a predetermined potential to the dummy drawing wiring. With this arrangement, a deviation of detection sensitivities of electrostatic capacitances of detection wirings can be reduced.